1. Field of the Invention
The invention relates to a drive assist control apparatus.
2. Description of the Related Art
Electric power steering systems (EPSs) are known in which a torque generated by a motor is applied to a steering mechanism of a vehicle to assist a driver's steering operation. A steering system described in Japanese Patent Application Publication No. 2014-40178 (JP 2014-40178 A) includes a first model that sets a target steering torque based on a steering angle and a second model that sets a target steered angle based on a steering torque. A control apparatus controls the motor based on both models (ideal models).
Recent EPSs are equipped with a system such as an advanced driver assistance system (ADAS) or a lane keeping assist (LKA) that assists the driver's operation. In some of the electric power steering systems, the motor is controlled based on the sum of the amount of control resulting from the driver's steering and the amount of control resulting from a drive assist for the purpose of improving the driver's steering feeling and providing an accurate drive assist.
In the electric power steering apparatuses that control the motor based on the sum of the amount of control resulting from the driver's steering and the amount of control resulting from a drive assist, a lateral acceleration acts on the vehicle due to the driver's steering and the drive assist. The lateral acceleration deteriorates the driver's steering feel. The amount of control performed by the motor may be reduced to decrease the lateral acceleration. However, a simple reduction in the amount of control performed by the motor reduces not only the amount of control resulting from the drive assist but also the amount of control resulting from the driver's steering. Accordingly, the driver's steering operation cannot be sufficiently assisted.